JP5583861B2 - Zoom lens and imaging device - Google Patents

Description

  The present invention relates to a zoom lens and an imaging apparatus, and more particularly to a zoom lens suitable for use in a digital camera, a video camera, and the like and an imaging apparatus including the zoom lens.

  In recent years, with the spread of personal computers to general households, digital cameras that can input image information such as photographed landscapes and human images to personal computers have become widespread. Recently, digital cameras have become more sophisticated, and accordingly, there is a demand for a digital camera equipped with a zoom lens that can shoot well over a wide-angle range.

  For this reason, for example, as in the zoom lenses described in Patent Document 1 and Patent Document 2, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a positive lens A zoom lens that includes a third lens group having a refractive power and performs zooming by changing the interval between the groups is used. Further, as a zoom lens having a basic configuration similar to those of Patent Documents 1 and 2, Patent Document 3 discloses that a small Fno. Have been disclosed.

JP 2003-107348 A JP 2009-156905 A JP 2011-81185 A

  However, in recent years, it has a wide angle and a small Fno. There is also a growing demand for zoom lenses that can reduce the overall length of the zoom lens. Patent Document 1 and Patent Document 2 describe Fno. Is larger, so that even smaller Fno. There is a need for a lens having Moreover, since the ratio of the length of the lens whole length with respect to image size is large in the thing of patent document 3, shortening of the lens whole length is calculated | required more.

  The present invention has been made in view of the above circumstances, and has a wide angle and a small Fno. An object of the present invention is to provide a zoom lens that maintains high optical performance and realizes shortening of the overall length of the zoom lens, and an imaging device including the zoom lens.

The zoom lens according to the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. And the distance between the first lens group and the second lens group is reduced and the second lens group and the third lens group are reduced in zooming from the wide-angle end to the telephoto end. A zoom lens in which at least the first lens group and the second lens group move along the optical axis so that the distance between the first lens group and the second lens group has a positive refractive power in order from the object side. A cemented lens composed of a lens, a 22nd lens having a positive refractive power and a 23rd lens having a negative refractive power, a 24th lens having a positive refractive power, and a 25th lens having a negative refractive power. Equations (1) and (2 And it is configured to satisfy.
-0.9 <fw / f25 <0 (1)
−0.40 <(R15 + R16) / (R15−R16) <2.40 (2)
However,
fw: focal length at the wide-angle end of the entire lens system f25: focal length of the 25th lens R15: paraxial radius of curvature of the object side surface of the 25th lens R16: near the image side surface of the 25th lens Axial curvature radius.

  In the present invention, each “lens group” includes not only a plurality of lenses but also a lens group.

In addition, the above-mentioned “consisting essentially of three lens groups” means that the imaging lens of the present invention has substantially no power other than the three lens groups, a lens such as a diaphragm or a cover glass. Other optical elements, lens flange, lens barrel, image sensor, camera shake correction mechanism, etc.
It is meant to include those with etc.

In the zoom lens according to the present embodiment, it is more preferable that the following conditional expressions (1-1) and (2-1) are satisfied.
−0.78 <fw / f25 <−0.14 (1-1)
−0.35 <(R15 + R16) / (R15−R16) <0.30 (2-1)
However,
fw: focal length at the wide-angle end of the entire lens system f25: focal length of the 25th lens R15: paraxial radius of curvature of the object side surface of the 25th lens R16: near the image side surface of the 25th lens Axial curvature radius.

In the zoom lens according to the present embodiment, it is preferable that the following conditional expression (3) is satisfied, and it is more preferable that the following conditional expression (3-1) is satisfied.
0.02 <D14 / fw <0.3 (3)
0.09 <D14 / fw <0.25 (3-1)
However,
D14: Distance on the optical axis between the 24th lens and the 25th lens fw: The focal length at the wide angle end of the entire lens system.

In the zoom lens according to the present embodiment, it is preferable that the following conditional expression (4) is satisfied, and it is more preferable that the following conditional expression (4-1) is satisfied.
0.15 <D12 / fw <0.6 (4)
0.20 <D12 / fw <0.52 (4-1)
However,
D12: Distance on the optical axis between the 23rd lens and the 24th lens fw: The focal length at the wide-angle end of the entire lens system.

  In the zoom lens according to the present embodiment, it is preferable that at least one of the twenty-first lens and the twenty-fourth lens is an aspherical surface.

In the zoom lens according to the present embodiment, it is preferable that the following conditional expression (5) is satisfied.
ω> 38 (5)
However,
ω: The half angle of view at the wide-angle end.

  An image pickup apparatus according to the present invention includes the zoom lens according to the present invention described above.

  According to the zoom lens of the present invention, in order from the object side, the first lens group having negative refractive power, the second lens group having positive refractive power, and the third lens group having positive refractive power. Consists of substantially three lens groups, and in zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is narrowed and the distance between the second lens group and the third lens group is reduced. Is a zoom lens in which at least the first lens group and the second lens group move along the optical axis so that the second lens group has, in order from the object side, a 21st lens having a positive refractive power, By comprising a cemented lens consisting of a 22nd lens having a refractive power of 23 and a 23rd lens having a negative refractive power, a 24th lens having a positive refractive power, and a 25th lens having a negative refractive power, There is a small Fn . And high optical performance that realizes shortening of the overall length of the zoom lens can be realized. As a result, it is possible to provide a zoom lens capable of realizing an image size larger than that of the conventional zoom lens while shortening the overall length of the zoom lens.

  Further, according to the zoom lens of the present invention, by satisfying the conditional expression (1), the power of the second lens group can be maintained well, the zoom lens can be shortened and the Fno. Can be realized. In addition, when the zoom lens according to the present invention further satisfies the conditional expression (1-1), it is possible to obtain the effect more remarkably.

  Further, when the zoom lens according to the present invention satisfies the conditional expression (2), it is possible to suitably suppress the curvature of field. In addition, when the zoom lens according to the present invention further satisfies the conditional expression (2-1), it is possible to obtain the effect more remarkably.

  In addition, when at least one surface of each of the 21st lens and the 24th lens is an aspherical surface, it is possible to correct spherical aberration more suitably by making at least one surface of the 21st lens an aspherical surface. In particular, astigmatism can be more preferably corrected by making at least one surface of the twenty-fourth lens an aspherical surface.

  Furthermore, in the present invention, when the conditional expression (3) is satisfied, the power of the second lens group is preferably maintained, so that the astigmatism is favorably corrected and the overall length of the zoom lens is shortened and the zoom lens is corrected. It is possible to shorten the collapsed thickness. Furthermore, in the present invention, when the conditional expression (3-1) is satisfied, the same effect can be obtained more remarkably. In the present invention, when the conditional expression (4) is satisfied, the power of the second lens group is suitably maintained, so that the entire length of the zoom lens can be shortened while the astigmatism is favorably corrected, and the zoom lens The thickness when retracted (collapse thickness) can be shortened. Furthermore, in the present invention, when the conditional expression (4-1) is satisfied, the same effect can be obtained more remarkably. Furthermore, in the present invention, when the conditional expression (5) is satisfied, it is possible to photograph suitably in a wide angle range.

  Further, according to the imaging apparatus of the present invention, since the high-performance imaging lens of the present invention is provided, it is possible to reduce the size of the entire apparatus and to obtain a captured image with higher image quality. it can.

Sectional drawing which shows the lens structure of the zoom lens concerning Example 1 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 2 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 3 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 4 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 5 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 6 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 7 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 8 of this invention. Sectional view showing the lens configuration of a zoom lens according to Example 9 of the present invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 10 of this invention. 11A to 11L are aberration diagrams of the zoom lens according to Example 1 of the present invention. 12A to 12L are graphs showing aberrations of the zoom lens according to Example 2 of the present invention. 13A to 13L are aberration diagrams of the zoom lens according to Example 3 of the present invention. 14A to 14L are graphs showing aberrations of the zoom lens according to Example 4 of the present invention. 15A to 15L are graphs showing aberrations of the zoom lens according to Example 5 of the present invention. FIGS. 16A to 16L are aberration diagrams of the zoom lens according to Example 6 of the present invention. 17A to 17L are aberration diagrams of the zoom lens according to Example 7 of the present invention. FIGS. 18A to 18L are diagrams showing aberrations of the zoom lens according to the eighth embodiment of the present invention. 19A to 19L are aberration diagrams of the zoom lens according to Example 9 of the present invention. 20A to 20L are graphs showing aberrations of the zoom lens according to Example 10 of the present invention. 1 is a front perspective view of an imaging apparatus according to an embodiment of the present invention. 1 is a rear perspective view of an imaging apparatus according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a configuration of a zoom lens according to an embodiment of the present invention, and corresponds to a zoom lens of Example 1 described later. 2 to 10 are cross-sectional views showing the configurations of zoom lenses according to Examples 2 to 10, which will be described later. The basic configuration of the zoom lens shown in FIGS. 1 to 10 is the same, and the method of illustration is also the same. Therefore, the zoom lens shown in FIG. 1 will be mainly described below as an example.

  Here, the left side of FIG. 1 is the object side, and the right side is the image side. FIG. 1 shows the lens arrangement at the wide-angle end for focusing at infinity at the upper stage, the lens arrangement for focusing at infinity at the intermediate position at the middle stage, and the lens at infinity focusing at the telephoto end in the lower stage. The arrangement is shown, and the schematic movement trajectory of each lens group at the time of zooming is indicated by a solid curve between the upper stage and the interruption, and between the interruption and the lower stage.

  The zoom lens shown in FIG. 1 includes, in order from the object side along the optical axis Z, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. The first lens group G1 and the second lens group G2 are reduced in distance in zooming from the wide-angle end to the telephoto end. At least the first lens group G1 and the second lens group G2 are configured to move along the optical axis Z so that the distance between the second lens group and the third lens group G3 is increased. That is, in this zoom lens, in the zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 and the distance between the second lens group G2 and the third lens group G3 change. An aperture stop St is disposed between the first lens group G1 and the second lens group G2.

  For example, the zoom lens of the example shown in FIG. 1 moves so as to draw a locus indicated by an arrow in the drawing at the time of zooming from the wide-angle end to the telephoto end. Further, the distance between the third lens group G3 and the image plane 100 also changes during zooming. In the zoom lens of the example shown in FIG. 1, the aperture stop St is configured to move integrally with the second lens group G2 at the time of zooming.

  Further, the aperture stop St shown in FIG. 1 does not necessarily indicate the size or shape, but indicates the position on the optical axis Z.

  When a zoom lens is applied to an imaging apparatus, a cover glass, an infrared cut filter, a low-pass filter is provided between the most image-side lens and the imaging surface (imaging surface) 100 according to the configuration of the camera side on which the lens is mounted. It is preferable to arrange various filters such as a filter. FIG. 1 shows an example in which a parallel plate-like optical member PP assuming these is arranged on the image side of the third lens group G3.

  In the example illustrated in FIG. 1, for example, when this zoom lens is applied to an imaging apparatus, the imaging surface of the imaging element is disposed on the imaging surface 100.

  The configuration of each lens group of the zoom lens shown in FIG. 1 will be described in detail below.

  The first lens group G1 has a negative refractive power as a whole. Here, the first lens group G1 includes an eleventh lens L11, which is a meniscus lens having a negative refractive power with a convex surface facing the object side in order from the object side, and a meniscus having a negative refractive power with a convex surface facing the object side. The lens includes a twelfth lens L12 as a lens and a thirteenth lens L13 having a positive refractive power with a convex surface facing the object side. Here, both surfaces of the thirteenth lens L13 are aspheric.

  The second lens group G2 has a positive refractive power as a whole. The second lens group G2 includes, in order from the object side, a cemented lens including a twenty-first lens L21 having a positive refractive power, a twenty-second lens L22 having a positive refractive power, and a twenty-third lens L23 having a negative refractive power. The 24th lens L24 which has refracting power, and the 25th lens L25 which has negative refracting power. In the second lens group G2, at least one surface of each of the 21st lens L21 and the 24th lens L24 is preferably an aspherical lens. Here, both surfaces of the 21st lens L21 and the 24th lens L24 are aspherical.

  The third lens group G3 has a positive refractive power as a whole. The third lens group G3 includes a thirty-first lens L31 having a positive refractive power.

The zoom lens is configured to satisfy the following conditional expressions (1) and (2).
-0.9 <fw / f25 <0 (1)
−0.40 <(R15 + R16) / (R15−R16) <2.40 (2)
However,
fw: focal length at the wide-angle end of the entire lens system f25: focal length of the 25th lens R15: paraxial radius of curvature of the object side surface of the 25th lens R16: paraxial radius of curvature of the image side surface of the 25th lens

Further, this zoom lens preferably satisfies the following conditional expressions (3) to (5). In addition, as a preferable aspect, it may satisfy any one of conditional expressions (3) to (5), or may satisfy any combination.
0.02 <D14 / fw <0.3 (3)
0.15 <D12 / fw <0.6 (4)
ω> 38 (5)
However,
D14: Distance on the optical axis between the 24th lens and 25th lens D12: Distance on the optical axis between the 23rd lens and 24th lens fw: Focal length at the wide angle end of the entire lens system ω: Half field angle at the wide angle end

  In the zoom lens, as the material disposed closest to the object side, specifically, glass is preferably used, or transparent ceramics may be used.

  Glass may be used as a lens material for forming an aspherical shape, or plastic may be used. When plastic is used, it is possible to reduce weight and cost.

  The zoom lens is preferably provided with a protective multilayer coating. In addition to the protective coat, an antireflection coating film for reducing ghost light during use may be applied.

  In the example shown in FIG. 1, an example in which the optical member PP is disposed between the lens system and the imaging surface is shown, but instead of disposing a low-pass filter, various filters that cut a specific wavelength range, or the like, These various filters may be disposed between the lenses, or a coating having the same action as the various filters may be applied to the lens surface of any lens.

  Further, the aperture stop St may be disposed at any position as long as it is between the most image side surface of the first lens group and the most image side surface of the second lens group. It is not limited to. For example, the aperture stop may be fixed at the time of zooming, or may be moved separately from the lens group.

  The operation and effect of the zoom lens configured as described above will be described.

  As described above, the zoom lens shown in FIG. 1 includes negative, positive, and positive first to third lens groups in order from the object side. In zooming from the wide-angle end to the telephoto end, the zoom lens shown in FIG. The distance between the lens groups changes so that at least the first lens group and the second lens group move along the optical axis so that the distance between the lens groups becomes narrower and the distance between the second lens group and the third lens group becomes wider. A zoom lens, which is a cemented lens comprising, in order from the object side, a second lens group, a twenty-first lens having a positive refractive power, a twenty-second lens having a positive refractive power, and a twenty-third lens having a negative refractive power , A 24th lens having a positive refractive power and a 25th lens having a negative refractive power, so that it has a wide angle and a small Fno. And high optical performance that realizes shortening of the overall length of the zoom lens can be realized. In particular, since the second lens group G2 has five lenses, a small Fno. By making the twenty-fifth lens L25 a lens having negative refractive power, shortening of the overall length of the lens system is suitably realized. In contrast, for example, in Patent Document 1 and Patent Document 2, Fno. Is a big one.

  Furthermore, according to the above configuration, the power of each lens group can be optimized, so that the overall length of the zoom lens can be shortened, and a larger image size such as a 2/3 inch type can be accommodated. A zoom lens can be realized. Accordingly, it is possible to meet the development requirement of applying an image sensor of a larger size in order to improve the image quality of a digital camera or the like. On the other hand, for example, in the zoom lens described in Patent Document 3, since the overall length of the zoom lens is relatively long with respect to the image size, the 2/3 inch type while keeping the overall length of the zoom lens compact. An image size corresponding to a large image sensor such as can not be realized.

  Furthermore, the first lens group G1 is an eleventh lens L11, which is a meniscus lens having a negative refractive power with a convex surface facing the object side, and a first meniscus lens having a negative refractive power, with a convex surface facing the object side. By comprising the 12 lenses L12 and the thirteenth lens L13 having positive refractive power with the convex surface facing the object side, the thickness (length in the optical axis direction) of the first lens group G1 can be reduced. The overall length of the zoom lens can be shortened. In addition, since at least one surface of the thirteenth lens L13 is aspherical, astigmatism over the entire zoom range and distortion at the wide angle end can be corrected well. In the zoom lens shown in FIG. 1, since both surfaces of the thirteenth lens L13 are aspherical surfaces, astigmatism in the entire zoom range and distortion at the wide-angle end can be corrected more preferably.

  Further, in the second lens group G2, the 22nd lens L22 having a positive refractive power and the 23rd lens L23 having a negative refractive power are used as a cemented lens, so that the distance between the 22nd lens L22 and the 23rd lens L23 is increased. It can be almost zero, and the 22nd lens L22 and the 23rd lens L23 are eccentrically arranged at positions deviated from the intended positions, so that good imaging characteristics cannot be obtained in a part of the photographed image. Occurrence of the blur problem can be suppressed. Further, by using the 22nd lens L22 and the 23rd lens L23 as a cemented lens, it is sufficient that the maximum allowable dimension and the minimum allowable dimension are satisfied with respect to the cemented lens obtained by adding the 22nd lens L22 and the 23rd lens L23. The above quality control is easy. On the other hand, when the 22nd lens L22 and the 23rd lens L23 are not cemented, it is necessary to manufacture each lens so as to satisfy the maximum allowable dimension and the minimum allowable dimension individually.

  In addition, when at least one surface of each of the 21st lens and the 24th lens is an aspherical surface, it is possible to correct spherical aberration more suitably by making at least one surface of the 21st lens an aspherical surface. In particular, astigmatism can be more preferably corrected by making at least one surface of the twenty-fourth lens an aspherical surface. In FIG. 1, since both surfaces of the 21st lens and the 24th lens are aspheric surfaces, spherical aberration and astigmatism can be corrected more suitably.

  When the third lens group G3 has a single lens configuration, it is possible to contribute to shortening the overall length of the entire zoom lens, which is preferable. Further, the cost can be reduced by suppressing the number of lenses of the third lens group G3.

Conditional expression (1) defines a preferable range of the ratio of the focal length fw at the wide-angle end of the entire zoom lens and the focal length f25 of the 25th lens L25. If the lower limit of conditional expression (1) is not reached, the power of the 25th lens L25 becomes strong and the power as the second lens group G2 tends to become weak, and a small Fno. It is difficult to achieve a lens configuration that can achieve Small Fno. In order to achieve the above, it is conceivable to increase the length (thickness) of the 25th lens L25 on the optical axis. However, in this case, the total length of the zoom lens tends to increase, which is not preferable. When the lower limit of conditional expression (1) is exceeded, a small Fno. If it is intended to realize a configuration that shortens the overall length of the zoom lens, it is difficult to sufficiently suppress field curvature. If the upper limit of conditional expression (1) is exceeded, the power of the 25th lens L25 becomes weak, so it becomes difficult to correct spherical aberration occurring in the second lens group G2, and astigmatism is also corrected. Not easy. Therefore, by configuring the 25th lens L25 and the other lens groups so as to satisfy the conditional expression (1), it is possible to satisfactorily correct field curvature, spherical aberration, and astigmatism, and a zoom lens. The zoom lens Fno. Can be reduced. From this viewpoint, in order to obtain better optical performance, the numerical range of the conditional expression (1) is
−0.78 <fw / f25 <−0.14 (1-1)
It is preferable that

Conditional expression (2) defines a preferable range of the curvature radius R15 on the image side and the curvature radius R16 on the object side in the paraxial axis of the 25th lens L25 in the second lens group G2. If the lower limit of conditional expression (2) is exceeded, field curvature tends to occur on the underside, which is not preferable. On the other hand, if the upper limit of conditional expression (2) is exceeded, field curvature tends to occur on the over side, which is not preferable. For this reason, field curvature can be satisfactorily suppressed by configuring the image-side and object-side radii of curvature in the paraxial axis of the 25th lens L25 so as to satisfy the conditional expression (2). From this viewpoint, the numerical range of conditional expression (2) is
−0.35 <(R15 + R16) / (R15−R16) <0.30 (2-1)
Is more preferable.

Conditional expression (3) defines a preferable range of the ratio between the distance D14 on the optical axis between the 24th lens L24 and the 25th lens L25 in the second lens group G2 and the focal length fw at the wide angle end of the entire zoom lens. To do. If the lower limit of conditional expression (3) is exceeded, the power of the second lens group G2 tends to be weak. In this case, it is conceivable to increase the amount of movement of the second lens group G2 at the time of zooming in order to achieve a sufficient zooming ratio. However, in order to achieve a sufficient zooming ratio, the entire length of the zoom lens can be increased. This is not preferable because it causes an increase. If the upper limit is exceeded, the power of the second lens group G2 tends to be strong, which is advantageous for shortening the overall length of the zoom lens, but it is difficult to suppress astigmatism. Further, since the length of the second lens group G2 in the optical axis direction is increased, the retractable thickness of the zoom lens is likely to increase, which is not preferable. Therefore, by configuring the distance on the optical axis between the 24th lens L24 and the 25th lens L25 and the focal length at the wide angle end of the entire zoom lens so as to satisfy the conditional expression (3), It is possible to easily maintain the power, to easily shorten the entire length of the zoom lens and the retractable thickness, and to easily correct astigmatism. From this viewpoint, in order to obtain better optical performance, the numerical range of the conditional expression (3) is
0.09 <D14 / fw <0.25 (3-1)
It is preferable that

Conditional expression (4) defines a preferable range of the ratio between the distance D12 on the optical axis between the 23rd lens L23 and the 24th lens L24 in the second lens group G2 and the focal length fw at the wide angle end of the entire zoom lens. To do. If the lower limit of conditional expression (4) is not reached, the power of the second lens group G2 tends to be weak. In this case, it is conceivable to increase the amount of movement of the second lens group G2 at the time of zooming in order to achieve a sufficient zooming ratio. However, in order to achieve a sufficient zooming ratio, the entire length of the zoom lens can be increased. This is not preferable because it causes an increase. If the upper limit is exceeded, the power of the second lens group G2 tends to be strong, which is advantageous for shortening the overall lens length, but it is difficult to suppress astigmatism. Further, since the length of the second lens group G2 in the optical axis direction is increased, the retractable thickness of the zoom lens is likely to increase, which is not preferable. Therefore, by configuring the distance on the optical axis between the 23rd lens L23 and the 24th lens L24 and the focal length at the wide angle end of the entire zoom lens so as to satisfy the conditional expression (4), the second lens group It is possible to easily maintain the power, to easily shorten the entire length of the zoom lens and the retractable thickness, and to easily correct astigmatism. From this viewpoint, in order to obtain better optical performance, the numerical range of the conditional expression (4) is
0.20 <D12 / fw <0.52 (4-1)
It is preferable that

  Conditional expression (5) defines a preferable range of the half angle of view ω at the wide-angle end. If the lower limit of conditional expression (5) is not reached, it is difficult to photograph up to a wide-angle range. Therefore, by satisfying conditional expression (5), it is possible to realize a zoom lens capable of photographing up to a wide angle range.

  As described above, according to the zoom lens of the present embodiment, the lens configuration of the zoom lens having the three-group configuration is optimized, and by satisfying appropriate conditional expressions as appropriate, a wide angle and a small Fno. And high optical performance that realizes shortening of the overall length of the zoom lens can be realized. As a result, it is possible to provide a zoom lens capable of realizing an image size larger than that of the conventional zoom lens while shortening the overall length of the zoom lens. Further, according to the imaging apparatus equipped with the zoom lens according to the present embodiment, it is possible to reduce the size of the entire apparatus while maintaining good imaging performance capable of imaging up to a wide-angle range.

  Next, numerical examples of the zoom lens according to the present invention will be described. The lens sectional views of the zoom lenses of Examples 1 to 10 are shown in FIGS. 1 to 10, respectively.

  Tables 1 to 3 below show specific lens data corresponding to the configuration of the imaging lens shown in FIG. Specifically, Table 1 shows lens data of the zoom lens according to Example 1, Table 2 shows aspheric data, and Table 3 shows zoom data and specification data. Similarly, lens data, aspheric surface data, and zoom data of the zoom lenses according to Examples 2 to 10 are shown in Tables 4 to 30. In the following, the meaning of the symbols in the table will be described using Example 1 as an example, but the same applies to Examples 2 to 10.

  In the lens data of Table 1, Si indicates the i-th (i = 1, 2, 3,...) Surface number that sequentially increases toward the image side with the most object-side component surface being first, and Ri is The radius of curvature of the i-th surface is indicated, and Di indicates the surface interval on the optical axis Z between the i-th surface and the i + 1-th surface. The bottom column of the surface interval indicates the surface interval between the final surface and the imaging surface in the table. Further, in the lens data of Table 1, Ndj is the first object-side lens, and the d-line (wavelength 587) of the j-th optical element (j = 1, 2, 3,...) Increases sequentially toward the image side. .6 nm) and νdj represents the Abbe number of the j-th optical element with respect to the d-line. The lens data includes the aperture stop St and the optical member PP. In the column of the radius of curvature of the surface corresponding to the aperture stop St, (aperture stop) is described. The radius of curvature of the lens data is positive when convex on the object side and negative when convex on the image side.

  In the lens data in Table 1, the interval changes at the time of zooming, the interval between the first lens group G1 and the second lens group G2, the interval between the second lens group G2 and the aperture stop St, the second lens group G2 and the third lens. DD [6] (variable), DD [, respectively, are provided in the columns of the group G3 interval, the third lens group G3 and the optical member PP, and the surface interval corresponding to the interval between the optical member PP and the image plane. 16] (variable), DD [18] (variable), DD [20] (variable). In the third embodiment, only DD [6] (variable) and DD [16] (variable) are variable.

In the lens data in Table 1, the surface number of the aspheric surface is marked with *, and the paraxial radius of curvature is shown as the radius of curvature of the aspheric surface. The aspheric surface data in Table 2 shows the surface number Si of the aspheric surface and the aspheric coefficients related to these aspheric surfaces. The aspheric coefficient is a value of each coefficient KA, Am (m = 3, 4, 5,... 20) in the aspheric expression represented by the following expression (6).
^{Zd = C · h 2 / {} 1+ (1-KA · C 2 · h 2) 1/2} + ΣAm · h m ... (6)
However,
Zd: Depth of aspheric surface (length of a perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis where the aspherical vertex contacts)
h: Height (distance from the optical axis to the lens surface)
C: Reciprocal KA of paraxial radius of curvature, Am: aspheric coefficient (m = 3, 4, 5,... 20)

  Table 3 shows scaling data and specification data. The zoom data shown in Table 3 shows f of the entire system at the wide-angle end, the middle, and the telephoto end, and the values of the surface spacings DD [6], DD [16], DD [18], and DD [20]. . The specification data shown in Table 3 includes zoom magnification (magnification ratio), focal length f, back focus Bf (air conversion distance), F number Fno. And the value of the total angle of view 2ω.

  Units Ri, Di, f in Table 1, units f, DD [6], DD [16], DD [18], DD [20] in Table 3, units Zd, h in formula (A) , "Mm" can be used. However, since the optical system can be used even with proportional enlargement or proportional reduction, the unit is not limited to “mm”, and other appropriate units can be used. The unit of the total angle of view 2ω in Table 1 is degrees.

  Table 31 shows values corresponding to the conditional expressions (1) to (5) in Examples 1 to 10. As can be seen from Table 31, Examples 1 to 10 all satisfy conditional expressions (1) to (5).

  FIGS. 11A to 11D show aberration diagrams of spherical aberration, astigmatism, distortion (distortion aberration), and magnification aberration (chromatic chromatic aberration of magnification) at the wide angle end of the zoom lens of Example 1. FIGS. 11 (E) to 11 (H) show aberration diagrams of spherical aberration, astigmatism, distortion (distortion aberration), and magnification aberration in the intermediate region of zooming of the zoom lens of Example 1, and FIG. FIGS. 11A to 11L show aberration diagrams of spherical aberration, astigmatism, distortion (distortion aberration), and magnification aberration at the telephoto end of the zoom lens of Example 1. FIGS.

  Each aberration diagram showing spherical aberration, astigmatism, and distortion (distortion aberration) shows aberrations with the d-line (wavelength 587.6 nm) as the reference wavelength. In the spherical aberration diagram, the aberrations for the d-line, C-line (656.3 nm), and F-line (wavelength 486.1 nm) are shown by a solid line, a broken line, and a dotted line, respectively. In the astigmatism diagram, sagittal and tangential aberrations are indicated by a solid line and a dotted line, respectively. In the magnification aberration diagram, aberrations with respect to the C line (656.3 nm) and the F line (wavelength 486.1 nm) are indicated by a broken line and a dotted line, respectively. Fno. Of spherical aberration diagram. Means F number, and ω in other aberration diagrams means half angle of view.

  Similarly, aberrations at the wide-angle end, middle, and telephoto end of the zoom lens of Example 2 are shown in FIGS. 12A to 12L, and at the wide-angle end, intermediate, and telephoto end of the zoom lens of Example 3. Each aberration is shown in FIGS. 13 (A) to 13 (L), and each aberration at the wide-angle end, middle, and telephoto end of the zoom lens of Example 4 is shown in FIGS. 14 (A) to 14 (L). 15A to 15L show the aberrations at the wide-angle end, the middle, and the telephoto end of the zoom lens of Example 5, and the aberrations at the wide-angle end, the middle, and the telephoto end of the zoom lens of Example 6 are shown. FIGS. 17A to 17L show aberrations at the wide-angle end, the middle, and the telephoto end of the zoom lens according to the seventh embodiment shown in FIGS. 16A to 16L, and the zoom according to the eighth embodiment. The aberrations at the wide-angle end, the middle, and the telephoto end of the lens are shown in FIGS. 18 (A) to 18 (L). 19A to 19L show the aberrations at the wide-angle end, the middle, and the telephoto end of the zoom lens of Example 9, and the aberrations at the wide-angle end, the middle, and the telephoto end of the zoom lens of Example 10 are shown. As shown in FIG.

  From the above data, the zoom lenses of Examples 1 to 10 are small and have a high magnification of about 3.8 times, and a small Fno. It can be seen that it has high optical performance to realize high image quality.

  Next, an embodiment of the imaging apparatus of the present invention will be described. 21A and 21B are a front perspective view and a rear perspective view of the digital camera 10 which is an embodiment of the imaging apparatus of the present invention, respectively.

  As shown in FIG. 21A, a digital camera 10 includes a zoom lens 12 according to an embodiment of the present invention, an objective window 13a of a finder, and a flash light emitting device 14 for emitting a flash to a subject. And are provided. Also, a shutter button 15 is provided on the upper surface of the camera body 11, and an imaging element 16 such as a CCD or a CMOS that captures an image of a subject formed by the zoom lens 12 is provided inside the camera body 11. .

  Further, as shown in FIG. 21B, on the back surface of the camera body 11, an LCD (Liquid Crystal Display) 17 for displaying images and various setting screens, a viewfinder observation window 13b, and a zoom lens 12 are changed. Zoom lever 18 and operation buttons 19 for performing various settings are provided. The digital camera 10 is configured such that the subject light guided through the front viewfinder objective window 13a is visible through the back viewfinder observation window 13b.

  The zoom lens 12 is disposed so that the optical axis direction thereof coincides with the thickness direction of the camera body 11. As described above, since the zoom lens 12 of the present embodiment has a sufficient shortening of the entire length of the zoom lens, the total length of the optical system in the optical axis direction when the zoom lens 12 is retracted and accommodated in the body of the camera body 11 is as follows. As a result, the digital camera 10 can be made thin. In addition, since the zoom lens 12 of the present embodiment has a wide angle and high optical performance, the digital camera 10 can shoot with a wide angle of view and can obtain a good image.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, the values of the radius of curvature, the surface spacing, the refractive index, the Abbe number, etc. of each lens component are not limited to the values shown in the above numerical examples, but can take other values.

  In the zoom lens of the present invention, the lens group that moves at the time of zooming and the direction thereof are not necessarily limited to the above examples.

In the above-described embodiment, the digital camera is described as an example of the imaging device. However, the present invention is not limited to this, and can be applied to other imaging devices such as a video camera and a surveillance camera. .

Claims (9)

In order from the object side, there are substantially three lens units each including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. At least in order to reduce the distance between the first lens group and the second lens group and increase the distance between the second lens group and the third lens group in zooming from the wide-angle end to the telephoto end. A zoom lens in which the first lens group and the second lens group move along the optical axis,
The second lens group includes, in order from the object side, a cemented lens including a twenty-first lens having a positive refractive power, a twenty-second lens having a positive refractive power, and a twenty-third lens having a negative refractive power, and a positive refractive power. And a 25th lens having a negative refractive power, and satisfying the following conditional expressions (1) and (2):
-0.9 <fw / f25 <0 (1)
−0.40 <(R15 + R16) / (R15−R16) <2.40 (2)
However,
fw: focal length at the wide-angle end of the entire lens system f25: focal length of the 25th lens R15: paraxial radius of curvature of the object side surface of the 25th lens R16: near the image side surface of the 25th lens Axial curvature radius. The zoom lens according to claim 1, wherein the following conditional expressions (1-1) and (2-1) are satisfied.
−0.78 <fw / f25 <−0.14 (1-1)
−0.35 <(R15 + R16) / (R15−R16) <0.30 (2-1) The zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied.
0.02 <D14 / fw <0.3 (3)
However,
D14: The distance on the optical axis between the 24th lens and the 25th lens. The zoom lens according to claim 3, wherein the following conditional expression (3-1) is satisfied.
0.09 <D14 / fw <0.25 (3-1) The zoom lens according to claim 1, wherein the following conditional expression (4) is satisfied.
0.15 <D12 / fw <0.6 (4)
However,
D12: The distance on the optical axis between the 23rd lens and the 24th lens. The zoom lens according to claim 5, wherein the following conditional expression (4-1) is satisfied.
0.20 <D12 / fw <0.52 (4-1)
And   The zoom lens according to any one of claims 1 to 6, wherein at least one of the twenty-first lens and the twenty-fourth lens is an aspherical surface. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied.
ω> 38 (5)
However,
ω: The half angle of view at the wide-angle end.   An imaging apparatus comprising the zoom lens according to claim 1.

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